No Headlights Runng Lights or dashlights

1989 c2500 2wd P/U - Driving home from work I went to flip dimmer switch and the headlights shut off until I hit the switch again. The next time I drove it at night the headlights, running lights and dashboard were not working. Could it be just be the light switch ? I didn't get to check anything out yet because it just happened tonight. Any suggestions?